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Aviation History
1988
1988 - 0091.PDF
Ariane 5 will have multiple satellite launch capability 45 per cent in the cost per orbital kilo gramme compared with Ariane 44L over eight launches. Production will support up to ten missions a year. The design will have growth potential with a view to further cutting launch costs, improving performance (by introducing the H10 second stage, once in the initial Ariane 5 proposal), or increasing safety and reliability. The new launcher comprises a first stage and two solid rocket boosters which are mission-independent. The design is , simplified, reducing the main mission events *and consequently improving reliability. An upper stage, a Matra vehicle equip ment bay (VEB), a Contraves fairing and, if required, a Dornier Structure Porteuse Externe de Lancements Triples Ariane (Speltra), or an Ariane 4 Spelda, complete the upper composite for automatic launches. .;. For manned launches the upper composite is replaced by Hermes and its adapter and its modified stage. In answer to critics, supporters of Ariane 5 point out that this never-the-twain approach of the two upper composites does not therefore compromise Ariane 5's commercial chances the least bit. The prime contractor for Ariane 5 is Aerospatiale. The Aerospatiale first stage comprises the cryogenic H155 with its 104-tonne-thrust HM60 engine from SEP. The 5 • 4m-diameter, 30m-long stage holds 130 tonnes of liquid oxygen and 25 tonnes of liquid hydrogen. Its dry weight is 15 tonnes. The H155 is designed for low-cost pro duction and operation, minimising risks and increasing reliability. This has I resulted in a simple engine with no "nice FLIGHT INTERNATIONAL, 16 January 1988 to have" features such as throttle—or 1980s technology—which would have increased complexity and cost. For simplicity, Esa has gone for a gas generator, an open-cycle engine, and a low development risk by using technology first tried on the German V2. The Ariane 2-4 HM7B third-stage engine is designed the same way, so SEP is relying on tried and tested technology. "In order to keep the highly visible 'up front', and hence politically sensitive development, costs for Ariane 5 down," says Webb, "the least innovative engineering has been used, particularly the engine design and final configuration. In this approach, probably the greatest mistake of all is associating a conservative design with low technical risk and, indeed, low operational risk." The two Aerospatiale P230 solid rocket boosters, each with 230 tonnes of solid propellant, deliver a thrust of 750 tonnes at lift off. The propulsion contractor is Europropulsion of Frapce and Italy. The P230s are each 3m in diameter, 30m high and weigh 269 tonnes. The 5-4m-diam- eter, 4-5m-long MBB/Erno LE5 second stage weighs 6 tonnes and carries 1-.7 tonnes of monomethyl hydrazine and 3 • 5 tonnes of nitrogen tetroxide; hypergolic propellants that ignite spontaneously on contact with each other. The LE5 engine^ has a thrust of 2 tonnes. The H155 will splash down well out to sea, but on Hermes and some other •• unmanned launches the stage will have to be deorbited without using its full performance by using remaining gases in the tanks. The deorbiting of the LE5 and the Matra VEB will be achieved by computer control. The P230s will be recovered from the ocean for inspection and, perhaps, eventual refurbishment. Compromising its commercial ability is the fact that Ariane has not only to be perfectly interfaced with the Columbus and Hermes elements, but also easily adaptable for commercial payloads. It has to be compatible mechanically, aero- dynamically, and electrically with Hermes, with which it will form a composite quite different from that used in automatic and commercial missions using the VEB. In particular, Hermes houses the elec trical equipment needed for flight control and guidance, replacing the VEB. A propulsion module based on the L5, called the L5B, will be fitted in the Hermes adapter to place it into a transfer orbit before the engine of Hermes itself performs the circularisation burn. Special fairings and adapters will be needed for the Columbus elements. A new launch complex, ELA 3, will be built at Kourou by prime contractor Cnes, with the pad connected by rail to the prep aration zone. Up to ten launches a year should be possible and, to make it less vulnerable to launch catastrophes, the design of the pad will be simplified as much as possible. Launch operations will be limited to the final stages of the count down, with much preparation and integ ration taking place in a dedicated prepara tion zone. Separate buildings will be constructed for solid-propellant handling. There will be four main areas: the P230 integration building, the launcher integration build ing, the final assembly building for payload integration, and the launch pad itself. Uniquely, ELA 3—and the other pads— will also have its own liquid hydrogen production plant and an air separation plant producing liquid oxygen and liquid nitrogen. Traditionally, launch complexes such as the Kennedy Space Centre have relied on trucked-in liquid hydrogen. Logistics, maritime transport, and road facilities will be enhanced to support oper ations. ELA 3 will also be used for full test firings of the HM60/H155. Since the Ariane 5 preparatory programme was given the go-ahead at the Esa Council meeting in Rome in January 1985, much work has already been com pleted. This includes technological work on critical components of the HM60 engine, such as bearings and turbines, the definition of hardware, and the fabrication and full development and acceptance of the liquid hydrogen turbopump test stand at SEP-Vernon and a chamber test stand at SEP/DFVLR-Lapoldhausen. System level and dependability assess ments and studies of subassemblies have been completed. Solid rocket booster barrel sections have been developed. Solid propellant has been chosen, and its fabri cation has begun. The large-dimension nozzle of the HM60 and its flexible nlounting have been developed, and the ihsulating material for the H155 has been chosen. An optimum solution for the injector for the 20kN engine for the LE5 has been found, and a detailed study of the launch system has been completed. S3 37
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